The project came to be, because everyone else appearently found it logical to use week numbers for planning. I didn't, so I needed an easier sollution, than to google "Calendar week numbers" every single time someone used this anoying system. So I decided on making a monthly wallpaper.
I wanted the wallpapers to follow the same pattern, but still change along with the world outside my window. I ended up having several for each month, allowing me to rotate between them.
I'm so sorry to have forgotten all the sources, but they were all either my own or from sxc.hu, and I don't think any where restricted in any way.
A (delayed) 2012 calendar is in the works.